It’s normal. Lead oxide, not tin. Don’t lose any sleep over it.
Yep, and the hotter you run your pot the more oxidation will occur.
I did buy a lead casting thermometer. Still trying to figure the "eye ball" settings on the turkey fryer ball valve to correspond to pot temp. Obviously all the way open for initial melt. My large pot will hold about 25 lbs of lead. SO, need to run 3 rotations of ingots thru the two Lyman ingot molds that I have for a single melt. After the second flux, trying to balance the temp to have a clean pour out of the ladle without the lead cooling off and starting to string into the mold. Versus too hot. The last melt, while waiting to for second round of ingots to solidify before I dumped them, it was starting to form the "purple/gold" looking stuff on top (too hot). All of that went into a few scrap ingots that I will remelt when I start up again.
Again, I appreciate everyone's input. It is a learning process...
